WhyloWhylo

Sky & space · Ages 3–9

Why does the moon seem to follow us?

The Moon is so far away that a short walk or drive barely changes the direction we look to see it. Nearby trees pass quickly, while the distant Moon seems to stay beside us.

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For little wonderers, ages 3–5

The Moon isn't chasing you. It is very far away! You move past nearby things quickly, but the Moon still looks almost in the same place.

A little deeper, ages 6–9

Moving changes our view of nearby objects much more than distant ones. This apparent shift is called parallax. The Moon does move around Earth, but the following effect during a short journey is mostly about distance and our changing viewpoint.

A Whylo Sample Story

The moon comes home too

Onthewayhome,LilanoticedapaleMoonabovetherooftops.Shewaved.Atthenextcorner,itwasstillthere.Shewalkedpastthebakery.Stillthere.‘Dad,’shewhispered,‘IthinktheMoonwantstocomehomewithus.’

Dadstoppedbesideabench.‘Let'swatchwhathappensaswewalk.’Lilachoseanearbylamppost,adistanthill,andtheMoon.Astheymoved,thelamppostslippedbehindthem.Thehillseemedtomovemuchless.TheMoonhardlyseemedtochangeitsplaceatall.

‘Nearthingsshiftinourviewalot,’Dadsaid.‘Farawaythingsshiftmuchless.TheMoonismuchfartherawaythanthathill.’Lilalookedbackatthelamppost.Ithadn'trunoff,either.Shehadmoved.‘SotheMooncanlooklikeit'scomingwitheverybody?’‘Lotsofpeoplecanhavethatsamefeeling.’

Lilaimaginedchildrenonotherstreetslookingupfromtheirownwalks.Perhapssomebodywascarryingaloafofbread.Perhapssomebodyhadaredscooter.TheycouldallfeelasthoughtheMoonhadchosentheirroute.

Athome,sheplacedhershoesneatlybesidethedoor.‘Youcan'tcomeinside,’shetoldtheMoonthroughthewindow.‘Butyoucanstayoutthere.’Thensheadded,‘Iknowyou'renotreallyfollowingme.It'sstillnicetoseeyou.’

Lila and Dad walk home beneath the Moon, past a lamp post and distant hills.
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On the way home, Lila noticed a pale Moon above the rooftops. She waved. At the next corner, it was still there. She walked past the bakery. Still there. ‘Dad,’ she whispered, ‘I think the Moon wants to come home with us.’

Dad stopped beside a bench. ‘Let's watch what happens as we walk.’ Lila chose a nearby lamp post, a distant hill, and the Moon. As they moved, the lamp post slipped behind them. The hill seemed to move much less. The Moon hardly seemed to change its place at all.

‘Near things shift in our view a lot,’ Dad said. ‘Faraway things shift much less. The Moon is much farther away than that hill.’ Lila looked back at the lamp post. It hadn't run off, either. She had moved. ‘So the Moon can look like it's coming with everybody?’ ‘Lots of people can have that same feeling.’

Lila imagined children on other streets looking up from their own walks. Perhaps somebody was carrying a loaf of bread. Perhaps somebody had a red scooter. They could all feel as though the Moon had chosen their route.

At home, she placed her shoes neatly beside the door. ‘You can't come inside,’ she told the Moon through the window. ‘But you can stay out there.’ Then she added, ‘I know you're not really following me. It's still nice to see you.’

What we learned

Nearby objects shift more in our view as we move. The very distant Moon seems to stay with us.

One more little discovery

Stand safely indoors. Hold a thumb at arm's length and look at it against a distant wall. Close one eye, then the other. Notice how the thumb seems to shift against the background.

Talk about it together

On a walk, which seems to pass you faster: a nearby fence or a distant hill?

Our characters and adventures are fictional. Explore the science behind this question:

Caltech Cool Cosmos: Why Does the Moon Follow Me?

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